The present invention relates generally to a wastewater cleaning system and more particularly to a system for cleaning industrial, agricultural or municipal water.
The present invention is related to the invention disclosed in U.S. Pat. No. 4,093,516 to Long, issued Jun. 6, 1978, the specification of which is incorporated by reference. The typical process of cleaning crude sewage involves filtration. The filtration process results in two separated parallel flows, one of which consists of sediment, and the other of filtrate. The filtrate is then aerated by air or oxygen in order to oxidize organic contaminants and is then allowed to settle for a period of time. Formed sediment is mixed with sediment collected after preliminary filtration and then converted into liquid fuel. Settled water from the filtrate is decanted and sterilized resulting in treated water. However, the preliminary filtration and subsequent aeration leads to increasing the concentration of dissolved and fine suspended substances which cannot be separated easily from water in the following steps of cleaning.
In U.S. Pat. No. 5,514,282, to Hibbard et all., issued May 6, 1996, solids.contained in wastewater are separated by air flotation by means of adding some coagulators, for example, iron salts and polymeric flocculates. In addition, after the flotation process wastewater is cleaned by multistage filtration using first a fine filter and then an ultrafilter.
However, treated water needs additional cleaning before it may be used for municipal or industrial consumption because it contains too many dissolved contaminants.
In U.S. Pat. No. 5,520,435, to Fink, issued Jun. 9, 1996, wastewater is treated first by the separation of liquid from solid. This process results in increasing the concentration of dissolved and fine suspended substances in treated water.
In U.S. Pat. No. 5916437, to Levitin, issued Jun. 9, 1999, domestic sewage after the initial settling process, forms two parallel flows, one containing liquid and crude sediment (0.2 mm and greater) and the other containing liquid and fine particles (less than 0.2 mm). The two flows are treated separately. As a result pure water, fertilizer, liquid fuel, and gas fuel containing mainly methane, is obtained. During this process some valuable compounds contained in the domestic and industrial wastewater could be lost in the treatment process.
Therefore, in previous patents the treated water requires additional complicated cleaning processes before use for domestic or industrial consumption.
In conclusion, a need exists for developing an economical and effective wastewater cleaning system producing treated water with the degree of purity that can be used for domestic and industrial consumption.
The present invention provides treatment of wastewater containing oil, some industrial organic compounds such as urea, as well as inorganic compounds. The resulting products will be purified water, dry fertilizer, pure carbomide, uncontaminated liquid and gas fuel, and other products that can be separated from the concentrate after ultrafiltration. In order to accomplish these and other objectives the present-invention improves the system for cleaning wastewater by subjecting the wastewater to a magnetic field and then heating it before the initial settling process. In addition, before ultrafiltration, the liquid is treated in an electroflotation device. The first settling process results in the formation of two separate parallel flows:
1. settled wastewater containing water-soluble compounds such as salts and urea;
2. sediment containing insoluble solids.
More specifically, a preferred embodiment of the present invention includes a settler with an inlet through which raw wastewater is introduced, and two outlets, through one of which settled wastewater is discharged and another through which sediment containing solids is discharged; a heater with an outlet through which the heated settled wastewater is discharged; a magnetic device with an outlet through which heated settled wastewater is discharged; a low-pressure separator for separating small-sized solid particles and oil droplets by flotation with air bubbles generated into the settled heated wastewater when the intake pressure becomes lower than ambient atmospheric pressure; a pump lowering the intake pressure relative to ambient pressure in the low-pressure separator, which is achieved by draining pretreated wastewater formed after treatment in the low-pressure separator; a pre-heater for heating pretreated wastewater; an aerator for oxidizing organic compounds contained in the pretreated wastewater; an electroflotation device for treating the pretreated wastewater by an electrical current; an ultrafilter for the final cleaning of treated wastewater discharged from the aerator resulting in the production of the effluent wastewater; a sterilizer of the effluent wastewater resulting in the production of pure water; a liquid fuel storage tank for holding liquid fuel produced in the low-pressure separator; a methane tank for the biochemical treatment of the sediment discharged from the settler and the low-pressure separator, resulting in the production of gas fuel containing mostly methane; a gas storage tank for holding gas fuel discharged from the methane tank; a drying disinfecting apparatus for the disinfecting and drying of solids discharged from the methane tank and the ultrafilter, resulting in the production of solid fertilizer; and a condenser for the purpose of condensing steam produced from the drying, disinfecting apparatus. Thereafter, the condensate formed is discharged into the sterilizer.
The wastewater cleaning system can be further comprised of a urea separator with two inlets through one of which the sediment from the low-pressure separator is introduced and the other through which needed reagents to improve the separation of urea are introduced from a dosing apparatus, and two outlets, through one of which flows the separated urea which is discharged to a drying and packaging apparatus and through the other of which sediment formed in the urea separator is introduced to the pump.
Another embodiment of the present invention includes a tank for holding the concentrate formed in the ultrafilter.
The above and other objects, features, and advantages of the present invention will become apparent to persons skilled in the art, especially when considered with the following description of the preferred embodiment, to be read in conjunction with the accompanying drawings.